U.S. patent number 4,471,192 [Application Number 06/224,557] was granted by the patent office on 1984-09-11 for microwave heating apparatus.
This patent grant is currently assigned to Osaka Gas Kabushiki Kaisha. Invention is credited to Kenichi Abe, Hidenori Awata, Masatsune Harada, Takehiro Shimizu.
United States Patent |
4,471,192 |
Awata , et al. |
September 11, 1984 |
**Please see images for:
( Certificate of Correction ) ** |
Microwave heating apparatus
Abstract
A microwave heating apparatus of a dielectric heating system
used in combination with a radiant heat source. A leakage waveguide
group is formed by arranging a number of leakage waveguides, each
having at least in one side surface thereof an electric wave
radiation opening which may be in the form of a long slit; and the
same is closed at each electric wave radiation opening thereof with
heat resistant non-metal material such as Teflon, glass or the like
and is arranged so that a heating medium such as hot air, steam or
the like may be passed therethrough. According to this
construction, as compared with a conventional microwave heating
apparatus of this kind, the heating energy is more sufficiently
consumed in an object to be heated, so that the heating speed can
be improved and the available space in the heating chamber can be
enlarged.
Inventors: |
Awata; Hidenori (Takarazuka,
JP), Harada; Masatsune (Torishima, JP),
Shimizu; Takehiro (Setagaya, JP), Abe; Kenichi
(Omiya, JP) |
Assignee: |
Osaka Gas Kabushiki Kaisha
(Osaka, JP)
|
Family
ID: |
26376850 |
Appl.
No.: |
06/224,557 |
Filed: |
November 25, 1980 |
PCT
Filed: |
March 29, 1980 |
PCT No.: |
PCT/JP80/00056 |
371
Date: |
November 25, 1980 |
102(e)
Date: |
November 25, 1980 |
PCT
Pub. No.: |
WO80/02221 |
PCT
Pub. Date: |
October 16, 1980 |
Foreign Application Priority Data
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|
|
|
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Mar 31, 1979 [JP] |
|
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54-37711 |
Mar 31, 1979 [JP] |
|
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54-37712 |
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Current U.S.
Class: |
219/692; 219/681;
219/697; 34/246; 34/259 |
Current CPC
Class: |
H05B
6/782 (20130101); H05B 6/72 (20130101) |
Current International
Class: |
H05B
6/72 (20060101); H05B 6/78 (20060101); F26B
023/08 (); H05B 006/64 () |
Field of
Search: |
;219/1.55R,1.55A,1.55F |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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|
|
|
|
51-14737 |
|
May 1976 |
|
JP |
|
1117753 |
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Jun 1968 |
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GB |
|
Primary Examiner: Reynolds; B. A.
Assistant Examiner: Keve; Alfred S.
Attorney, Agent or Firm: Bloom; Leonard
Claims
We claim:
1. A microwave heating apparatus comprising at least one leakage
waveguide, said waveguide including a forward end portion and a
rearward end portion, said waveguide further including a side wall
having at least one microwave irradiating opening formed therein,
means including a heat-resistant non-metallic material for closing
said irradiating opening in said waveguide, microwave generating
means coupled to said forward end portion of said waveguide,
heating medium generating means coupled to said forward end portion
of said waveguide, and means including a material covering said
rearward end portion, said last-named means precluding passage of
the microwave energy through said rearward end portion but
permitting passage of the heating medium therethrough out of said
waveguide.
2. The microwave heating apparatus of claim 1, wherein a plurality
of said leakage waveguides are provided in parallel with each
other, wherein a common waveguide is connected to one side of said
waveguides, thereby forming a first comb assembly, and wherein a
common waveguide is connected to the other side of said waveguides,
thereby forming a second comb assembly meshing with said first comb
assembly.
3. The microwave heating apparatus of claim 2, wherein said
microwave generating means is connected to said first comb
assembly, and wherein another microwave generating means is
connected to said second comb assembly, whereby the microwave
energy enters said first and second comb assemblies from mutually
opposite directions.
4. The microwave heating apparatus of claim 1, wherein said
microwave irradiating opening comprises a long slit formed in the
longitudinal direction of said waveguide, said slit being gradually
wider towards said rearward end portion of said waveguide.
5. The microwave heating apparatus in any one of claims 1 through
4, further including a reflecting pan facing the microwave
irradiating opening, whereby foodstuffs to be heated may be
received in the pan.
6. The microwave heating apparatus in any one of claims 1 through
4, wherein at least two leakage waveguide groups are disposed in
plural stages, the adjacent group having a space therebetween.
7. The microwave heating apparatus of claim 2, further including
respective conduit pipes connecting said heating generating means
to said respective common waveguides, whereby a closed circuit is
formed for said heating medium.
8. The microwave heating apparatus of claim 1, wherein said leakage
waveguide is placed within a vacuum container.
Description
DESCRIPTION
TECHNICAL FIELD
This invention relates to a microwave heating apparatus which is
effective not only as a common heating apparatus but also
especially as a heating apparatus of a freeze-drying apparatus or a
vacuum-drying apparatus for foodstuff.
BACKGROUND ART
Freeze-drying or vacuum-drying for foodstuff can provide a produce
more excellent in quality than that by normal pressure heat drying,
and therefore is used reputably as a means of process for
preservation foodstuffs or space foodstuffs. However, there has
been adopted in that process a surface heat drying system by a
radiant heat source, so that if the radiant heat thereof is
increased in thermal volume in order to shorten the drying time,
the surface temperature of the foodstuff is raised to excess and
cells of the foodstuff are dried hard or tissue thereof is damaged,
and as a result the foodstuff is changed in color or flavor.
Accordingly, it has been necessary to take the drying time of 6-10
hours for obtaining a food product good in quality.
In view of this, the inventors of the present invention have
previously succeeded in shortening the drying time by using a
microwave heating apparatus capable of heating a material to be
heated from the central portion thereof, jointly with a radiant
heat source. However, the conventional microwave heating apparatus
is so arranged that an electric wave may radiate onto a material to
be heated substantially perpendicularly thereto, so that there is
involved such an inconvenience that an electric wave transmission
distance through the material to be heated is short and the heating
energy thereof is not effectively consumed. Additionally, the same
has to provide in a heating chamber a heat generating plate or the
like serving as a radiant heat source, so that there is involved
such an inconvenience that an effectively available space in the
heating chamber is small.
DISCLOSURE OF THE INVENTION
This invention has for its object to provide a microwave heating
apparatus free from those inconveniences, and it is characterized
in that a leakage waveguide group is formed by arranging a number
of leakage waveguides, each having at least in one side surface
thereof an electric wave radiation opening in the form of a long
slit or a series of openings spaced one from another (much in the
nature of "stepping stones"), and the same is closed at each
electric wave radiation opening thereof with heat resistant
non-metal material such as Teflon, glass or the like and is so
arranged that a heating medium such as hot air, steam or the like
may be directed or passed therethrough.
Thus, according to this invention, since the leakage waveguide
group is formed by arranging a number of leakage waveguides, each
having at least in one side surface thereof an electric wave
radiation opening in the form of a long slit or a series of spaced
openings, it is advantageous in that there can be removed the
foregoing inconveniences with the conventional microwave heating
apparatus in which an electric wave is radiated onto the material
to be heated substantially perpendicularly thereto, and that the
heating speed can be improved as compared with that in the
conventional one and the drying time can be shortened.
Additionally, the leakage waveguide group is closed at each
electric wave radiation opening thereof with the heat resistant
non-metal material such as Teflon, glass or the like and is so
arranged that a heating medium such as hot air, steam or the like
may be passed therethrough, and thus the leakage waveguide which
radiates an electric wave from the electric wave radiation opening
thereof is utilized as a thermal radiator, and consequently there
can be removed the foregoing inconvenience with the conventional
microwave heating apparatus of this kind in which a heat generating
plate or the like serving as a radiant heat source is provided in a
heating chamber, and thus it is advantageous in that there can be
provided such one that an available space in a heating chamber is
large, and there can be obtained practically a new type heating
apparatus which is high in industrial value.
Additionally, since it is so arranged that an electric wave may be
distributively radiated from the electrical wave radiation opening
such as a long slit or the like in the leakage waveguide, a
terminal voltage of the leakage waveguide is lowered, and
accordingly it is advantageous in that when this invention
apparatus is used as a heating apparatus of a vacuum-drying
container or apparatus, there is not generated such an electric
discharge as caused by the conventional microwave heating
apparatus, and consequently a heating capacity thereof can be kept
in nearly equal to that in the case of a common use thereof.
BRIEF DESCRIPTION OF THE FIGURES IN THE DRAWINGS
FIG. 1 is a vertically sectional front view of one exemplified
microwave heating apparatus of this invention,
FIG. 2 is a sectional view taken along the lines II--II in FIG.
1,
FIG. 3 is a perspective view, partly omitted, of a leakage
waveguide assembly and
FIG. 4 is a diagram showing the relations between the intensity of
an electric wave radiated from a slit which is an electric wave
radiation opening of a leakage waveguide and the distance of the
slit.
BEST MODE FOR CARRYING OUT THE INVENTION
An embodying example of this invention will be explained with
reference to the accompanying drawings.
Referring to FIGS. 1 to 3, numeral 1 denotes a leakage waveguide
assembly, and the assembly 1 is disposed in three stages in upper
and lower relationships.
The leakage waveguide assembly 1 is composed of a pair of right and
left leakage waveguide groups 2,2.
The leakage waveguide groups 2,2 are constructed to be in the form
of teeth of a comb in such a manner that a number of leakage
waveguides 4 (seven ones in the drawings) of each group are
connected through respective connecting slits 5 to each of
waveguides 3a,3b. And a pair of right and left ones 2,2 thereof are
disposed in such a manner that their comb teeth portions are
alternately brought to be in engagement one with another so that
form the leakage waveguide assembly 1 may be constructed.
The leakage waveguide 4 is provided in one side surface or wall
with at least one microwave irradiating opening formed therein.
Preferably, the opening comprises a slit 6 (formed in the
longitudinal direction of the waveguide as shown more clearly in
FIG. 2) and the slit 6 is provided on its upper surface or lower
surface with a closing plate 7 made of heat resistant non-metallic
material such as glass, Teflon or the like which permits an
electric wave to transmit therethrough. The leakage waveguides 4,4
are provided at their rearward end boundaries or portions between
the end portions and the waveguides 3a,3b, with electric wave
screen members 8,8 (which may be formed from) a metallic net or
other suitable material which preclude and do not permit an
electric wave to pass therethrough but which permit a heating
medium such as hot air, steam or the like to pass therethrough.
The waveguides 3a,3b are connected, respectively, with oscillation
apparatus 9,9 comprising magnetrons or the like, and are connected
through respective conduit pipes 1Oa,1Ob with a hot blast
generating apparatus 11 (or an apparatus for generating a heating
medium such as steam or the like) the respective conduit pipes
thereby forming a closed circuit for the heating medium as shown
more clearly in FIG. 2. Moreover, again as shown in FIG. 2, the
oscillation apparatus 9,9 comprising the microwave generating means
are so connected to the respective comb assemblies that the
microwave energy enters from mutually opposite directions.
Referring to FIG. 1, numeral 12 denotes a rack of grid form, and
numeral 13 denotes a metallic receiving pan which receives
foodstuffs to be heated 14 and is placed on the rack 12.
Since this invention apparatus is constructed as above, the
electric waves generated at the oscillation apparatus 9,9 are
passed into the leakage waveguides 4,4 of the comb teeth portions
after passed through the connecting slits 5,5 from the waveguides
3a,3b, and are radiated, as shown by arrows in FIG. 1, from the
slits 6 in an oblique direction at an angle determined by a free
space wave length and a transmission wave length of the electric
wave, and are reflected by the metallic receiving pan 13, and thus
the electric waves pass in the form of V through the interior of
the foodstuffs to be heated 14. As a result, the electric wave
transmission distance in the foodstuffs to be heated 14 is
elongated, and the heating energy of the electric wave is
sufficiently consumed therein, so that the foodstuffs to be heated
14 can be dried by heat for a short period of time as compared with
the case in the conventional apparatus.
The electric wave radiated from the long slit 6 is damped in its
intensity, as shown in FIG. 4. accordingly as it goes from the
connecting portion of the leakage waveguide 4 with each of the
waveguides 3a,3b towards its rearward end (the connecting portion
thereof with the waveguide 3a is on the left side and the
connecting portion thereof with the waveguide 3b is on the right
side in the same Figure.), so that the heating temperatures by the
respective electric waves are differentiated one from another at
the left portion and the right portion of the foodstuff to be
heated 14. However, since the leakage waveguides 4,4 in which the
electric wave advancing directions are in opposite one to another
are disposed alternately, the foodstuff to be heated 14 can be
heated nearly uniformly.
Additionally, the slit 6 is shaped into one which is gradually
larger in width towards its rearward end, that is, gradually wider
towards the rearward end portion of the respective waveguide so
that a damping degree of the electric wave that is damped
accordingly as it goes towards the rearward end of each of the
leakage waveguides 4,4 is smaller than that in the case of a slit
which is equal in width, and in this way the foodstuff to be heated
14 can be heated more uniformly if the shape of the slit is
properly designed.
Meanwhile, the hot air generated by the hot air generating
apparatus 11 is circulated as shown by shorter arrows in FIG. 2 in
order of the conduit pipe 1Oa.fwdarw.the waveguide 3a.fwdarw.the
leakage waveguides 4,4 . . . .fwdarw.the waveguide 3b.fwdarw.the
conduit pipe 1Ob.fwdarw.the hot air generating apparatus 11, so
that the leakage waveguides 4,4 . . . act as a thermal radiator and
the foodstuff to be heated 14 is heated by the heat radiated from
the surfaces thereof.
According to this apparatus, as above, the foodstuff to be heated
14 is heated from the center portion thereof by the electric wave
radiated from the slit 6 and at the same time is heated from the
surface thereof by the heat radiated from the leakage waveguide 4,
and thus by the cooperation thereof the same is dried faster than
not only by the conventional heating apparatus alone but also by
the microwave heating apparatus used together with a radiant heat
source.
In the foregoing example, the leakage waveguides 2,2 are arranged
so that the electric waves may be passed in the mutually opposite
directions and also the slit 6 is gradually wider towards the
rearward end thereof, but it may be so modified that the electric
waves may be passed in the same directions and that the slit 6 may
be shaped so as to be equal in its width.
Further, the use of the metallic receiving pan 13 serving as an
electric wave reflecting plate may be abolished, and the lower
stage leakage waveguide group 2 is brought to be as nearest as
possible to the foodstuff to be heated 14 so that the upper side
surface thereof may serve as an electric wave reflecting plate.
Furthermore, the lower stage leakage waveguide 4 may be provided in
its upper side surface also with the slit 6, so that the foodstuff
to be heated 14 can be radiated by electric waves from above and
below.
Almost the same advantageous effect can be obtained even if the
electric wave radiation opening is in the form of stepping stones
as hereinbefore described.
Furthermore, if, though not illustrated, an adjusting plate for
adjusting the slit width is provided on one side surface of the
leakage waveguide 4 having the slit 6 so that the gradually larger
width condition of the slit 6 may be changed by the same, the
optimum heating suitable for the condition of the foodstuff to be
heated 14 can be obtained.
It will also be appreciated that, if desired, at least two leakage
waveguide groups may be disposed in plural stages, that is, stacked
up relative to one another with a space between adjacent
groups.
Obviously, many modifications may be made without departing from
the basic spirit of the present invention. Accordingly, it will be
understood by those skilled in the art that within the scope of the
appended claims, the invention may be practiced other than has been
specifically described herein.
* * * * *